1. Field of the Invention
The present invention relates to an electrophotographic image-forming member used in the field of image formation, which has a sensitivity to electromagnetic waves such as light (herein used in a broad sense, including ultraviolet rays, visible light, infrared rays, X-rays, gamma-rays and the like).
2. Description of the Prior Art
Se, Se-Te, CdS, ZnO, and organic photoconductive materials such as PVCz, TNF, and the like are well known as a photoconductive material constituting a photoconductive layer in an electrophotographic image-forming member. As disclosed, for example, German Laid-open Patent Application Nos. 2746967 and 2855718, amorphous silicon (hereinafter referred to as a-Si) has recently attracted attention as a hopeful photoconductive material in view of advantages that a-Si has comparable characteristics to other photoconductive materials in photosensitivity, spectral wave region, response to light, dark resistance, and the like as well as no harm to human bodies during usage and easy capability of controlling p-n in spite of amorphism.
As mentioned above, a-Si has various superior characteristics to other photoconductive materials, the practical application of which as an electrophotographic image-forming member is under rapid progress, although there still remain some points to be solved.
For example, in some cases, when applied in an image-forming member for electrophotrography, residual potential is observed to remain during use thereof. Therefore, when such image-forming member is repeatedly used for a long time, there are caused accumulation of electrical or photoconductive fatigue to cause so-called ghost phenomenon. In other words, there occur disadvantages such as whitening in transferred images and the like.
Further, in case of preparing a photoconductive layer in thickness of ten and several microns or more, after taking out the photoconductive member having such thick photoconductive layer from a vacuum-deposition chamber, the photoconductive layer tends to separate from or peel off the surface of the substrate, on which the photoconductive layer is laid, or to crack with the elapse of standing time. These phenomena are points to be solved in view of stability for time elapsed, since these phenomena frequently occure in the case of a cylindrical substrate used generally in the field of electrophotography, and in the like.
In view of the above-mentioned points, the present invention has succeeded in establishing, as a result of extensive and strenuous studies, a relationship between a photoconductive layer and a substrate on which the photoconductive layer is laid from the standpoints of mechanical, electrical, photoconductive, and durable characteristics of the photoconductive layer itself, in case that the photoconductive layer is prepared with an amorphous material [hereinafter referred to as a-Si(H, X)] which contains at least one of hydrogen atom (H) and halogen atom(X) in a matrix of silicon atom.
In other words, the present inventors observed that a large strain is generated in the layer of a-Si(H, X) upon forming it, and that the strain causes separation from, or peeling of a surface of a substrate, on which the layer is laid, or cracking. On account of this, they have found it necessary for eliminating of the above-mentioned disadvantages that the strain in the formed layer is removed or relaxed to the extent that it has no effect on the layer by any means, that mechanical and electrical contact between the substrate and the layer of a-Si is optimized, that closeness between them is improved, and that the optimum conditions satisfying concurrently the above-mentioned requires is set for obtaining an electrophotographic image-forming member having excellent durability. Establishment of such optimum conditions has been succeeded as a result of extensive and strenuous stuides.